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# Age, extent and carbon storage of the central Congo Basin peatland complex

## Abstract

Peatlands are carbon-rich ecosystems that cover just three per cent of Earth’s land surface1, but store one-third of soil carbon2. Peat soils are formed by the build-up of partially decomposed organic matter under waterlogged anoxic conditions. Most peat is found in cool climatic regions where unimpeded decomposition is slower, but deposits are also found under some tropical swamp forests2,3. Here we present field measurements from one of the world’s most extensive regions of swamp forest, the Cuvette Centrale depression in the central Congo Basin4. We find extensive peat deposits beneath the swamp forest vegetation (peat defined as material with an organic matter content of at least 65 per cent to a depth of at least 0.3 metres). Radiocarbon dates indicate that peat began accumulating from about 10,600 years ago, coincident with the onset of more humid conditions in central Africa at the beginning of the Holocene5. The peatlands occupy large interfluvial basins, and seem to be largely rain-fed and ombrotrophic-like (of low nutrient status) systems. Although the peat layer is relatively shallow (with a maximum depth of 5.9 metres and a median depth of 2.0 metres), by combining in situ and remotely sensed data, we estimate the area of peat to be approximately 145,500 square kilometres (95 per cent confidence interval of 131,900–156,400 square kilometres), making the Cuvette Centrale the most extensive peatland complex in the tropics. This area is more than five times the maximum possible area reported for the Congo Basin in a recent synthesis of pantropical peat extent2. We estimate that the peatlands store approximately 30.6 petagrams (30.6 × 1015 grams) of carbon belowground (95 per cent confidence interval of 6.3–46.8 petagrams of carbon)—a quantity that is similar to the above-ground carbon stocks of the tropical forests of the entire Congo Basin6. Our result for the Cuvette Centrale increases the best estimate of global tropical peatland carbon stocks by 36 per cent, to 104.7 petagrams of carbon (minimum estimate of 69.6 petagrams of carbon; maximum estimate of 129.8 petagrams of carbon2). This stored carbon is vulnerable to land-use change and any future reduction in precipitation7,8.

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from$8.99 All prices are NET prices. ## Change history • ### 01 February 2017 The Acknowledgements section was updated. ## References 1. 1 Rydin, H. & Jeglum, J. K. The Biology of Peatlands 230–233 (Oxford Univ. Press, 2006) 2. 2 Page, S. E., Rieley, J. O. & Banks, C. J. Global and regional importance of the tropical peatland carbon pool. Glob. Change Biol. 17, 798–818 (2011) 3. 3 Draper, F. C. et al. The distribution and amount of carbon in the largest peatland complex in Amazonia. Environ. Res. Lett. 9, 124017 (2014) 4. 4 Keddy, P. A. et al. Wet and wonderful: the world’s largest wetlands are conservation priorities. Bioscience 59, 39–51 (2009) 5. 5 Schefuß, E., Schouten, S. & Schneider, R. R. Climatic controls on central African hydrology during the past 20,000 years. Nature 437, 1003–1006 (2005) 6. 6 Verhegghen, A., Mayaux, P., de Wasseige, C. & Defourny, P. Mapping Congo Basin vegetation types from 300 m and 1 km multi-sensor time series for carbon stocks and forest areas estimation. Biogeosciences 9, 5061–5079 (2012) 7. 7 Haensler, A., Saeed, F. & Jacob, D. Assessing the robustness of projected precipitation changes over central Africa on the basis of a multitude of global and regional climate projections. Clim. Change 121, 349–363 (2013) 8. 8 James, R., Washington, R. & Rowell, D. P. Implications of global warming for the climate of African rainforests. Phil. Trans. R. Soc. Lond. B 368, (2013) 9. 9 Hughes, R. H. & Hughes, J. S. A Directory of African Wetlands 493, 547–557 (IUCN, 1992) 10. 10 Bouillenne, R., Moureau, J. & Deuse, P. Esquisse écologique des faciès forestiers et marécageux des bords du lac Tumba (Domaine de I’I. R. S. A. C., Mabali, Congo Belge) (Académie royale des Sciences Coloniales, 1955) 11. 11 Évrard, C. Recherches écologiques sur le peuplement forestier des sols hydromorphes de la Cuvette centrale congolaise 71, 73, 194 (INEAC, 1968) 12. 12 Bord na Móna. Fuel Peat in Developing Countries. World Bank Technical Paper No. 41 (The World Bank, 1985) 13. 13 Markov, V. D., Olunin, A. S., Ospennikova, L. A., Skobeeva, E. I. & Khoroshev, P. I. World Peat Resources (Nedra, 1988) 14. 14 Joosten, H., Tapio-Biström, M. L. & Tol, S. Peatlands - Guidance for Climate Change Mitigation Through Conservation, Rehabilitation and Sustainable Use. (FAO and Wetlands International, 2012) 15. 15 Shanahan, T. M. et al. The time-transgressive termination of the African Humid Period. Nat. Geosci. 8, 140–144 (2015) 16. 16 Lawson, I. T., Jones, T. D., Kelly, T. J., Coronado, E. N. H. & Roucoux, K. H. The geochemistry of Amazonian peats. Wetlands 34, 905–915 (2014) 17. 17 Lähteenoja, O. & Page, S. High diversity of tropical peatland ecosystem types in the Pastaza-Marañón basin, Peruvian Amazonia. J. Geophys. Res. Biogeosci. 116, G02025 (2011) 18. 18 Page, S. E., Rieley, J. O., Shotyk, O. W. & Weiss, D. Interdependence of peat and vegetation in a tropical peat swamp forest. Phil. Trans. R. Soc. Lond. B 354, 1885–1897 (1999) 19. 19 Runge, J. & Nguimalet, C. R. Physiogeographic features of the Oubangui catchment and environmental trends reflected in discharge and floods at Bangui 1911–1999, Central African Republic. Geomorphology 70, 311–324 (2005) 20. 20 Lee, H. et al. Characterization of terrestrial water dynamics in the Congo Basin using GRACE and satellite radar altimetry. Remote Sens. Environ. 115, 3530–3538 (2011) 21. 21 Jung, H. C. et al. Characterization of complex fluvial systems using remote sensing of spatial and temporal water level variations in the Amazon, Congo, and Brahmaputra Rivers. Earth Surf. Process. Landf. 35, 294–304 (2010) 22. 22 Bwangoy, J.-R. B., Hansen, M. C., Roy, D. P., De Grandi, G. & Justice, C. O. Wetland mapping in the Congo Basin using optical and radar remotely sensed data and derived topographical indices. Remote Sens. Environ. 114, 73–86 (2010) 23. 23 Hooijer, A. et al. Current and future CO2 emissions from drained peatlands in Southeast Asia. Biogeosciences 7, 1505–1514 (2010) 24. 24 Grace, J., Mitchard, E. & Gloor, E. Perturbations in the carbon budget of the tropics. Glob. Change Biol. 20, 3238–3255 (2014) 25. 25 Joosten, H. The Global Peatland CO2 Picture: Peatland Status and Emissions in All Countries of the World (Wetlands International, 2009) 26. 26 Alsdorf, D. et al. Opportunities for hydrologic research in the Congo Basin. Rev. Geophys. 54, 378–409 (2016) 27. 27 Ingram, H. A. P. Size and shape in raised mire ecosystems: a geophysical model. Nature 297, 300–303 (1982) 28. 28 Jaenicke, J., Rieley, J. O., Mott, C., Kimman, P. & Siegert, F. Determination of the amount of carbon stored in Indonesian peatlands. Geoderma 147, 151–158 (2008) 29. 29 Dommain, R., Couwenberg, J. & Joosten, H. Development and carbon sequestration of tropical peat domes in south-east Asia: links to post-glacial sea-level changes and Holocene climate variability. Quat. Sci. Rev. 30, 999–1010 (2011) 30. 30 Page, S. et al. A record of Late Pleistocene and Holocene carbon accumulation and climate change from an equatorial peat bog (Kalimantan, Indonesia): implications for past, present and future carbon dynamics. J. Quaternary Sci. 19, 625–635 (2004) 31. 31 Lähteenoja, O., Ruokolainen, K., Schulman, L. & Oinonen, M. Amazonian peatlands: an ignored C sink and potential source. Glob. Change Biol. 15, 2311–2320 (2009) 32. 32 Zhou, L. et al. Widespread decline of Congo rainforest greenness in the past decade. Nature 509, 86–90 (2014) 33. 33 Wetlands International. Peta Sebaran Lahan Gambut, Luas dan Kandungan Karbon di Kalimantan/Maps of Area of Peatlands Distribution and Carbon Content in Kalimantan 2000–2002 (Wildlife Habitat Canada, 2004) 34. 34 Centre Nationale de la Statistique et des Etudes Economiques du Congo. Population des Départements- Likuoalahttp://www.cnsee.org/index.php?option=com_content&view=article&id=135%3Apopdep&catid=43%3Aanalyse-rgph&Itemid=37&limitstart=9 (accessed 25 May 2016) 35. 35 Laraque, A., Bricquet, J. P., Pandi, A. & Olivry, J. C. A review of material transport by the Congo River and its tributaries. Hydrol. Processes 23, 3216–3224 (2009) 36. 36 Samba, G. & Nganga, D. Rainfall variability in Congo-Brazzaville: 1932–2007. Int. J. Climatol. 32, 854–873 (2012) 37. 37 Samba, G., Nganga, D. & Mpounza, M. Rainfall and temperature variations over Congo-Brazzaville between 1950 and 1998. Theor. Appl. Climatol. 91, 85–97 (2008) 38. 38 NASA/METI. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) version 2http://earthexplorer.usgs.gov/ (2011) 39. 39 Tachikawa, T. et al. ASTER Global Digital Elevation Model Version 2 - Summary of Validation Results (NASA, 2011) 40. 40 USGS. Shuttle Radar Topography Mission (SRTM) 1 arc-second Digital Elevation Model (DEM)http://earthexplorer.usgs.gov/ (2006) 41. 41 Keselman, H. J., Wilcox, R., Othman, R. & Fradette, A. R. K. Trimming, transforming statistics, and bootstrapping: circumventing the biasing effects of heterescedasticity and nonnormality. J. Mod. Appl. Stat. Methods 1, 38 (2002) 42. 42 Lewis, S. L. et al. Above-ground biomass and structure of 260 African tropical forests. Phil. Trans. R. Soc. Lond. B 368, 20120295 (2013) 43. 43 Feldpausch, T. R. et al. Tree height integrated into pantropical forest biomass estimates. Biogeosciences 9, 3381–3403 (2012) 44. 44 Goodman, R. C. et al. Amazon palm biomass and allometry. For. Ecol. Manage. 310, 994–1004 (2013) 45. 45 Chave, J. et al. Improved allometric models to estimate the aboveground biomass of tropical trees. Glob. Change Biol. 20, 3177–3190 (2014) 46. 46 Martin, A. R. & Thomas, S. C. A reassessment of carbon content in tropical trees. PLoS One 6, e23533 (2011) 47. 47 Zanne, A. E. et al. Data from: Towards a Worldwide Wood Economics Spectrum http://dx.doi.org/10.5061/dryad.234 (Dryad Digital Repository, 2009) 48. 48 Chave, J. et al. Towards a worldwide wood economics spectrum. Ecol. Lett. 12, 351–366 (2009) Download references ## Acknowledgements We thank the Wildlife Conservation Society Congo Programme for logistical support and the villages that hosted our fieldwork: Bokatola, Bolembe, Bondoki, Bondzale, Ekolongouma, Ekondzo, Itanga, Mbala and Moungouma. We thank F. Twagirashyaka, T. F. Moussavou, P. Telfer, A. Pokempner, J. J. Loumeto and A. Rahïm (logistics); R. Mbongo, P. Abia (deceased), T. Angoni, C. Bitene, J. B. Bobetolo, C. Bonguento, J. Dibeka, B. Elongo, C. Fatty, M. Ismael, M. Iwango, G. Makweka, L. Mandomba, C. Miyeba, A. Mobembe, E. B. Moniobo, F. Mosibikondo, F. Mouapeta, G. Ngongo, G. Nsengue, L. Nzambi and J. Saboa (field assistance); M. Gilpin, D. Ashley and R. Gasior (laboratory assistance); D. Quincy (remote sensing and GIS support); D. Harris, J. M. Moutsambote (plant identification); P. Gulliver (radiocarbon analyses); F. Draper (access to Peruvian data); and T. Kelly and D. Young (discussions). The work was funded by Natural Environment Research Council (CASE award to S.L.L. and G.C.D.; fellowship to E.M.; NERC Radiocarbon Facility NRCF010001 (alloc. no. 1688.0313 and 1797.0414) to I.T.L., S.L.L. and G.C.D.); Wildlife Conservation Society-Congo (to G.C.D.), the Royal Society (to S.L.L.), Philip Leverhulme Prize (to S.L.L.), and the European Union (FP7, GEOCARBON to S.L.L.; ERC T-FORCES to S.L.L.). JAXA, METI, USGS, NASA and OSFAC are acknowledged for collecting and/or processing remote sensing data. ## Author information ### Affiliations Authors ### Contributions S.L.L. conceived the study. G.C.D., S.L.L., I.T.L., S.A.I and S.E.P. developed the study. G.C.D. collected most of the data, assisted by B.E.Y., S.L.L. and I.T.L. Laboratory analyses were performed by G.C.D. G.C.D. and E.T.A.M. analysed the remotely sensed data. G.C.D., S.L.L., I.T.L., E.T.A.M. and S.E.P. interpreted the data. G.C.D. and S.L.L. wrote the paper, with input from all co-authors. ### Corresponding author Correspondence to Greta C. Dargie. ## Ethics declarations ### Competing interests The authors declare no competing financial interests. ## Additional information Reviewer Information Nature thanks J. Chambers, L. Fatoyinbo and the other anonymous reviewer(s) for their contribution to the peer review of this work. ## Extended data figures and tables ### Extended Data Figure 1 Peatland water table time-series data. a, b, Time series of water-table levels for the Ekolongouma (a) and Itanga (b) transects for the time period March 2013 to May 2014 (black, blue and red lines indicate different sample locations along the transects). c, d, Time series of water-table levels for the wet-season month of October 2013 for the Ekolongouma (c) and Itanga (d) transects, when river-caused flood events are more likely (left-hand axis; black, blue and red lines), and daily TRMM rainfall estimates (right-hand axis; purple lines). No obvious flood waves are seen. e, Relationship between the summed monthly cumulative increase in water table (CIWT) from 10 pressure transducers (Itanga, Ekolongouma, Bonzale and Bondoki transects), for months in which CIWT > 0, and summed monthly rainfall estimates for the same months from TRMM (best-fitting line: y = 0.959x − 133, R2 = 0.90, P < 0.001). Months during which the water table was not always above the peatland surface (CIWT ≤ 0) were excluded from the analysis, owing to large changes in the water table that obscure the relationship between water table and water input. Data from 10 pressure transducers are included, because two transducers had no months during which the water table was consistently above the peat surface. ### Extended Data Figure 2 Spatial distribution of the ground-truth points across the Cuvette Centrale. Main panel, ALOS PALSAR imagery of the Cuvette Centrale area and the spatial distribution of the ground-truth points (crosses for GPS, circles for Google Earth derived points) that were used as test and training data in the 1,000 runs of the maximum likelihood classifications used to estimate regional peat extent. The black boxes correspond to the other panels: a, the main study region; b, c, two regions within DRC where GPS ground-truth points were also obtained. ### Extended Data Figure 3 Relationship between estimates of peat depth using the field-pole method and those using peat cores followed by laboratory analysis, and the relationship between corrected peat depth and total peat carbon stocks. a, Relationship between peat depth (in m) estimated using a metal pole (rapid protocol) and estimated using coring and laboratory analysis (full protocol); LOI, loss-on-ignition; best-fitting line: y = 0.888x − 34.8, R2 = 0.97, P < 0.001, where y is cored peat depth and x is pole peat depth. The organic matter content of the core must be ≥65% to be classified as peat. Soft carbon-rich material that is <65% organic matter is captured using the rapid protocol, which lies beneath peat using our definition, but above the more typical mineral soil. b, Relationship between core depth (in m) and total carbon stocks (in Mg C ha−1) for cores from the Cuvette Centrale (best-fitting line: carbon stocks = 1,374 + 2,425log10(total core depth), R2 = 0.89, P < 0.0001). ### Extended Data Figure 4 Distribution of peatland carbon stock estimates. Estimated carbon stocks from 100,000 resamples of peatland area, peat depth and per-unit-area carbon storage. Median, 30.6 Pg C; mean, 29.8 Pg C; 95% CI, 6.3–46.8 Pg C. ## Supplementary information ### Supplementary Information This file contains Supplementary Methods and additional references. (PDF 311 kb) ## PowerPoint slides ### PowerPoint slide for Fig. 1 ### PowerPoint slide for Fig. 2 ## Rights and permissions Reprints and Permissions ## About this article ### Cite this article Dargie, G., Lewis, S., Lawson, I. et al. 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